Highest temperature in London on June 25?

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Market context

The real-world event centres on the highest temperature recorded at London City Airport on 25 June 2026, a date that historically falls within the UK’s warm season. For a power-user evaluating this market programmatically, the settlement hinges on a single data point from Wunderground, requiring automated scripts to fetch the daily maximum in Celsius and compare it against the predefined resolution ranges.

Historically, late June in London often sees highs between 20°C and 25°C, though recent anomalies have pushed temperatures higher. In May 2026, London Heathrow recorded 33.5°C, the hottest May temperature ever in the UK, while Hampstead hit 33.9°C on 23 June 2026, suggesting that extreme heat is no longer confined to summer peaks[4][9]. Given this trend, the current 0% YES probability for the highest range appears misaligned with recent volatility, framing the market as a potential utility for conditional order strategies.

Traders should monitor the Met Office’s daily forecasts and any emerging red heat warnings, as these act as direct catalysts for temperature spikes. The BBC forecast for 25 June predicts sunny conditions with a moderate breeze and a high of 22°C, but the rapid rise in recent days indicates dependencies on broader atmospheric patterns that could shift quickly[1][6]. A recent BBC News report on record-breaking heat underscores the need for real-time data integration in trading bots to capture such dependencies before settlement[4].

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page reviews Highest temperature in London on June 25? across five venues. We show live odds for Polymarket-based markets (sourced from the Polygon order book); for other venues we list platform attributes, since the comparable contracts are not exposed via a public API on every venue. Every CTA points at PolyGram — the application we operate, where you trade directly against the Polymarket order book at 0% fees.

Resolution & payout

Polymarket-based markets settle through the UMA Optimistic Oracle on Polygon. A proposer submits the outcome, a two-hour challenge window opens, and unchallenged proposals finalise the resolution. Payouts settle automatically in USDC the moment the result is final — no bookmaker, no delay.

Kalshi-based markets settle in USD via the CFTC-regulated clearinghouse. Betfair Exchange settles in GBP/EUR net of commission. Manifold is play-money and does not pay out real funds.

FAQ

Where can I trade this market with the lowest fees?

On PolyGram, which mirrors the Polymarket order book at 0% fees. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

How does resolution work?

Through the UMA Optimistic Oracle on Polygon: a proposer submits the outcome, a two-hour challenge window opens, and USDC payouts settle automatically once the result is final.

What's the difference between YES and NO shares?

A YES share pays $1.00 if the event happens, $0 otherwise. A NO share pays $1.00 if the event doesn't happen. The market price between 0¢ and 100¢ is the implied probability.

How fast are USDC deposits?

Polygon credits deposits after 12 confirmations — usually under 30 seconds. Withdrawals follow the same path and land back in your wallet within minutes.

Do I need to KYC for this market?

Not under $1,500 of lifetime trading volume. Above that threshold, PolyGram triggers a quick verification flow that finishes in minutes.